Electricity 5-7 (1)

```Electricity
1.
The diagram shows two dodgem cars at a fairground. The circuit symbols for the motor
and pedal for each dodgem car are shown on the diagram.
pick-up wire
connection
to wire mesh
wire
mesh
power
supply
connection
to metal
floor
metal floor
metal wheel
(a)
Complete the following sentence.
Each dodgem car is connected to the power supply through the
......................................... which is in contact with the wire
mesh, and through the ......................................... which is
in contact with the metal floor.
1 mark
(b)
Dodgem cars are connected using parallel circuits.
Complete the circuit diagram below for the two dodgem cars.
Use two motor symbols,
M
, and two switch symbols,
.
The power supply for the circuit has been drawn for you.
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connection
to wire mesh
power
supply
connection
to metal
floor
2 marks
(c)
Even when the power supply is switched on, the dodgem car will not move until
the pedal is pressed. Give the reason for this.
.....................................................................................................................
.....................................................................................................................
1 mark
(d)
A man looks after the dodgem cars during the rides.
Why does the man not get an electric shock as he walks across the metal floor?
.....................................................................................................................
.....................................................................................................................
1 mark
(e)
During one ride, the two dodgem cars are running. The pick-up wire on one car
snaps off. Describe how this affects:
(i)
the dodgem car with the broken pick-up wire;
.............................................................................................................
1 mark
(ii)
the other dodgem car.
.............................................................................................................
1 mark
Maximum 7 marks
2.
The back window of this car contains a heating element.
The heating element is part of an electrical circuit connected to the battery of the car.
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The diagrams below show two ways of connecting the circuit of a heating element.
circuit A
(a)
circuit B
Give the name of each type of circuit:
circuit A ...................................................................
circuit B ...................................................................
1 mark
(b)
A wire gets broken at point X on circuit A and at point Y on circuit B.
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Y
X
circuit A
circuit B
When the switch is closed, how does the broken wire affect the heating
element in:
(i)
circuit A? ............................................................................................
...........................................................................................................
1 mark
(ii)
circuit B? .............................................................................................
.............................................................................................................
1 mark
(c)
In very cold weather, ice may form on the back window of the car.
When the heating element is switched on, the ice will disappear and the surface
of the window will become clear and dry.
(i)
Fill the gap below to show the energy transfer that takes place.
When the heater is switched on, ........................................ energy is
transferred from the wires to the ice.
1 mark
(ii)
As the window becomes clear and dry, physical changes take place in the
ice.
Fill the gaps below to show the physical changes which take place.
from …………………. to ……………………….to ……………………
1 mark
Maximum 5 marks
3.
Imran built a puzzle circuit with three identical bulbs and a 3V battery.
He covered the connections to the bulbs with a piece of card as shown below.
The bulbs could be seen through holes in the card.
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3V battery
A
C
card
B
All the bulbs were on but their brightness was different.
Lucy removed bulbs A, B and C in turn. Before connecting each bulb back into the
circuit she observed the effect on the other two bulbs.
She recorded her observations in the table below.
(a)
bulb removed
observations
A
B and C stayed on
B
C went off
A stayed on
C
B went off
A stayed on
Complete the circuit diagram below to show how the three bulbs could be
connected.
Use your knowledge of series and parallel circuits, and the observations in the
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3V battery
A
C
B
2 marks
(b)
Imran used three identical bulbs but their brightness was different.
Which bulb was the brightest? Give the letter.
...............
Give the reason for your choice.
.....................................................................................................................
.....................................................................................................................
1 mark
(c)
Imran added a switch to the circuit so that he could turn all three bulbs
on and off at the same time.
Place a letter S on your circuit diagram where this switch could be placed.
1 mark
maximum 4 marks
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4.
Peter measured the current through each of three similar bulbs in a parallel circuit.
A1
A2
A3
He had only one ammeter and he placed it first at A1, then A2, then A3, in order to
measure the currents.
The table shows his results.
(a)
position of ammeter
current, in amps
A1
0.14
A2
0.16
A3
0.15
He expected the current readings to be the same for each bulb but found they
were different.
Suggest two reasons why the readings were different.
1. ................................................................................................................
2. ................................................................................................................
2 marks
(b)
Peter then measured the current at A4 and recorded it as 0.45 A. He concluded
that the current at A4 could be calculated by adding together the currents through
each of the bulbs at positions A1, A2 and A3.
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A4
He added two more similar bulbs to his circuit, in parallel. The current through
each bulb was 0.15 A.
Use Peter's conclusion to predict the current at A4 with the 5 bulbs in the circuit.
................ A
A4
1 mark
(c)
Peter left the circuit connected overnight. He used a datalogger to measure the
current at position A4 at regular intervals of time. The next morning the bulbs
were dim.
Using the axes below, sketch (do not plot) how the current at position A4 might
change with time.
Indicate on the graph:
(i)
The correct labels for each axis, including the correct units.
(ii)
The shape of the graph you would expect to obtain.
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0
0
2 marks
Maximum 5 marks
5.
Lorna built the circuit drawn below. All the bulbs are identical.
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(a)
Complete the table below by writing on or off for each bulb.
switch
bulb
S1
S2
A
B
open
open
off
off
open
closed
closed
open
closed
closed
3 marks
(b)
Lorna then built a different circuit as shown below.
How could Lorna get both bulbs to light at the same time in this circuit?
......................................................................................................................
......................................................................................................................
1 mark
maximum 4 marks
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